1. Surface-to-Surface Simulation
Workshop 11
Node-to-Node Elements
Surface-to-Surface Simulation
REFERENCE:
Training Manual
Node-to-Node Elements (7-12)

2. 11. Node-to-Node Elements Surface-to-Surface Simulation
Purpose
Demonstrate using the node-to-node contact elements to simulate surface-to-surface contact
Goal
Create 3D node-to-node contact elements and solve the small deflection contact analysis
Model Description
Applied pressure load
1/2 symmetry
applied pressure load
1/2 symmetry
5500 psi
0 psi
Beam #1
Beam #2
contact zone
E = 10E6 PSI
October 15, 2001
Inventory #
W11-2

3. 11. Node-to-Node Elements …Surface-to-Surface Simulation
STEPS TO FOLLOW:
1. Start an ANSYS Interactive session in the working directory specified by the instructor using “node-to-node” as the jobname
2. Resume the NODE-TO-NODE database
Utility Menu > File > Resume from
Select “node-to-node.db1”
[OK]
OR enter the following command:
RESUME, node-to-node, db1
NOTE: The node-to-node.db1 database contains the completed geometry, material, boundary condition, and loading definitions for this finite element model.
October 15, 2001
Inventory #
W11-3

4. 11. Node-to-Node Elements …Surface-to-Surface Simulation
3. Add 3D node-to-node contact element type
Main Menu > Preprocessor > Element Type > Add/Edit/Delete
[Add…]
Contact
3D nd-to-nd 178
Element type reference number = 3
[OK]
[Close]
OR enter the following commands:
/PREP7
ET, 3, CONTA178
October 15, 2001
Inventory #
W11-4

5. 11. Node-to-Node Elements …Surface-to-Surface Simulation
4. Define the real constant for the contact element
Main Menu > Preprocessor > Real Constants > Add/Edit/Delete…
[Add…]
Type 3 CONTA178
[OK]
Real Constant Set No. = 1
[Close]
OR enter the following command:
R, 1
NOTE: This will define the REAL constant and use the default values.
October 15, 2001
Inventory #
W11-5

6. 11. Node-to-Node Elements …Surface-to-Surface Simulation
5. Set the element attributes
Main Menu > Preprocessor > Create > Elements > Elem Attributes …
Element type number = 3 CONTA178
Material number = 1
Real constant set number = 1
[OK]
OR enter the following commands:
TYPE, 3
MAT, 1
REAL, 1
NOTE: The graphics window title bar contains the current element attribute settings.
October 15, 2001
Inventory #
W11-6

7. 11. Node-to-Node Elements …Surface-to-Surface Simulation
6. Create the node-to-node contact elements at the coincident nodes
Main Menu > Preprocessor > Create > Elements > At Coincid Nd…
Tolerance of coincidence =
Nodal number ordering “Low to high”
[OK]
[Pick All]
OR enter the following command:
EINTF,
7. Solve the contact analysis
Main Menu > Solution > Current LS
OR enter the following commands:
/SOLUTION
SOLVE
NOTE: If the CONTA178 nodes are coincident, you must specify the gap direction by means of real constants NX, NY, and NZ (the global Cartesian X, Y, and Z components of the gap direction vector).
For this model, the contact normal is parallel with the global Y axis. Therefore, the vector coordinates are: < NX, NY, NZ > = < 0, 1, 0 >
October 15, 2001
Inventory #
W11-7

8. 11. Node-to-Node Elements …Surface-to-Surface Simulation
8. Specify the contact normal direction vector
Main Menu > Preprocessor > Real Constants > Add/Edit/Delete…
Select “Set 1”
[Edit…]
Type 3 CONTA178
[OK]
Defined gap normal - X comp. NX = 0
Defined gap normal - Y comp. NY = 1
Defined gap normal - Z comp. NZ = 0
[Close]
OR enter the following command:
RMODIF, 1, 6, 0, 1, 0
October 15, 2001
Inventory #
W11-8

9. 11. Node-to-Node Elements …Surface-to-Surface Simulation
9. Solve the small displacement contact analysis
Main Menu > Solution > Current LS
[OK]
OR enter the following commands:
/SOLUTION
SOLVE
10. Select the solid elements for post-processing
Utility Menu > Select > Entities
Elements
By Elem Name
Element name = SOLID185
Choose “From Full”
ESEL, S, ENAME, , SOLID185
NOTE: CONTA178 elements do not support large deflection.
(The element maintains its original orientation in either a small or a large deflection analysis).
October 15, 2001
Inventory #
W11-9

10. 11. Node-to-Node Elements …Surface-to-Surface Simulation
11. Plot the von Mises stress
Main Menu > General Postproc > Plot Results > Nodal Solu
Stress
von Mises SEQV
[OK]
OR enter the following command:
/POST1
PLNSOL, S, EQV
October 15, 2001
Inventory #
W11-10

11. 11. Node-to-Node Elements …Surface-to-Surface Simulation
12. Select the contact elements for post-processing
Utility Menu > Select > Entities
Elements
By Elem Name
Element name = CONTA178
Choose “From Full”
[OK]
OR enter the following command:
ESEL, S, ENAME, , CONTA178
13. Define an element table (ETABLE) for the contact normal force (FN) and for the gap size (USEP).
Element Output Name
Item
Sequence Number
Name
Item E FN
SMISC 1
FSY 2
FSZ 3
STAT
NMISC
OLDST
USEP
ALPHA 4
BETA 5
UTY 6
UTZ 7 MU 8
ANGLE 9 KN 10 KS 11
TOLN 12
FTOL 13
SLTOL 14
NOTE: When you are defining ETABLEs you need to know the item and sequence number for the element output to be defined.
Each element description in the ANSYS Elements Reference has an "Element Output Definitions" table like the one shown here for CONTA178.
October 15, 2001
Inventory #
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12. 11. Node-to-Node Elements …Surface-to-Surface Simulation
13. (… ETABLE definition continued)
Main Menu > General Postproc > Element Table > Define Table
[Add]
User label for item = FN
By sequence num
SMISC
Enter 1 in selection box
[Apply]
User label for item = GAP
NMISC, 3
[OK]
[Close]
OR enter the following command:
ETABLE, FN, SMISC, 1
ETABLE, GAP, NMISC, 3
October 15, 2001
Inventory #
W11-12

13. 11. Node-to-Node Elements …Surface-to-Surface Simulation
14. Select all nodes attached to selected elements
Utility Menu > Select > Entities
Nodes
Attached to
Elements
Choose “From Full”
[Apply]
[Plot] …to plot the nodes
OR enter the following command:
NSLE
NPLOT
15. Turn on numeric contour labeling
Utility Menu > PlotCtrls > Numbering
SVAL Numeric contour values = On
[OK]
/PNUM, SVAL, 1
October 15, 2001
Inventory #
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14. 11. Node-to-Node Elements …Surface-to-Surface Simulation
16. Plot the contact normal forces
Main Menu > General Postproc > Element Table > Plot Elem Table
Item to be plotted = FN
Average at common nodes? = Yes – average
[OK]
OR enter the following command:
PLETAB, FN, AVG
October 15, 2001
Inventory #
W11-14

15. 11. Node-to-Node Elements …Surface-to-Surface Simulation
17. List the contact normal forces together with the gap size.
Main Menu > General Postproc > Element Table > List Elem Table
Item to be listed = FN
[OK]
OR enter the following command:
PRETAB, FN, GAP
NOTE: Review the extreme values for GAP. The negative values indicate an interference and a closed gap, where the maximum amount of penetration is virtually zero.
October 15, 2001
Inventory #
W11-15